The field of the disclosure relates generally to gas turbine engines and, more particularly, to an air guide to control air flow from an air/oil separator in a gas turbine engine.
Gas turbine engines typically include an air/oil separator (AOS), also known as deoilers, as part of a vented sump system to separate air that is intermixed with oil in the bearing compartments and gearboxes of the gas turbine engine. Separated air exits the AOS through a vent line in a high-speed free, that is, unforced-rotational, vortex in a hollow exit shaft. The exiting air travels at an axial speed downstream a length of the hollow shaft, while also swirling at a radial, or rotational, flow velocity around an inner circumference of the exit shaft. In the free vortex, the rotational flow velocity of the air is inversely proportional to the distance from the axial center of the hollow shaft, and thus the rotational velocity of the air traveling down the central axis of the hollow shaft is significantly higher in the rotational velocity of the air traveling near the inner circumference of the hollow shaft. This difference in rotational velocities in the free vortex creates air friction, which results in undesirable loss in pressure down the shaft.
At least some conventional AOS venting systems have been known to place baffles down the central axis of the hollow shaft in a radial cross configuration, thereby dividing the hollow shaft into four radial quadrants down its length. This approach, however, creates miniature vortexes in each of the quadrants, which are subject to undesirable pressure loss from vortex air friction. Additionally, the irregular radial shape is another source of air friction that contributes to pressure loss.